This invention relates in general to body and frame assemblies for vehicles. In particular, this invention relates to an improved structure for a closed channel structural member for use in such a vehicle body and frame assembly that includes an internal air tank for supplying pressurized air to an auxiliary device, such as an active suspension for the vehicle.
Many land vehicles in common use, such as automobiles, vans, and trucks, include a body and frame assembly that is supported upon a plurality of ground-engaging wheels by a resilient suspension system. The structures of known body and frame assemblies can be divided into two general categories, namely, separate and unitized. In a typical separate body and frame assembly, the structural components of the body portion and the frame portion of the vehicle are separate and independent from one another. When assembled, the frame portion of the assembly is resiliently supported upon the vehicle wheels by the suspension system and serves as a platform upon which the body portion of the assembly and other components of the vehicle can be mounted. Separate body and frame assemblies of this general type are found in most older vehicles, but remain in common use today for many relatively large or specialized use modern vehicles, such as large vans, sport utility vehicles, and trucks. In a typical unitized body and frame assembly, the structural components of the body portion and the frame portion are combined into an integral unit that is resiliently supported upon the vehicle wheels by the suspension system. Unitized body and frame assemblies of this general type are found in many relatively small modern vehicles, such as automobiles and minivans.
Traditionally, the various components of vehicular body and frame assemblies have been formed from open channel structural members, i.e., structural members that have a non-continuous cross sectional shape (such as U-shaped or C-shaped channel members, for example). For example, it is known to use one or more open channel structural members to form the side rails, the cross members, and other components of a ladder frame type of separate body and frame assembly. However, the use of open channel structural members to form the various components of vehicular body and frame assemblies has been found to be undesirable for several reasons. To address this, it has been proposed to form one or more of the components of the vehicular body and frame assemblies from closed channel structural members, i.e., structural members that have a continuous cross sectional shape (such as tubular or box-shaped channel members, for example). This cross sectional shape is advantageous because it provides strength and rigidity to the vehicle body and frame component. Also, closed channel structural members are well suited to be deformed to a desired shape by hydroforming, which is a well known process that uses pressurized fluid supplied within the closed channel structural member to deform it into conformance with a surrounding die. Hydroforming has been found to be a desirable forming process, because portions of a closed channel structural member can be quickly and easily deformed to have a complex cross sectional shape.
In some vehicles, an auxiliary device is provided that utilizes pressurized air as the actuating medium. For example, in some active suspension systems, pressurized air is utilized to selectively increase or decrease the dampening characteristics of the shock absorbers. Auxiliary systems of this general type typically include a tank or canister that is charged with a quantity of pressurized air. The tank of pressurized air functions as an accumulator that can provide a quantity of pressurized air to the auxiliary system immediately upon demand. Traditionally, the tank of pressurized air has been provided as a separate component that has been welded or otherwise secured to the vehicle frame assembly or other portion of the vehicle. Although effective, this arrangement has been found to consume an undesirable amount of physical space in the vehicle. Thus, it would be desirable to provide an improved structure for such a tank of pressurized air that consumes less space in the vehicle.